Before Moses died, he recalled to the Hebrews the commandments, the statutes, and the judgments(Deut 6:1) that the Lord wanted them to perform in the promised land. It was a lengthy discourse —nearly all of Deuteronomy — and included orders regarding the Amalekites:

Remember what Amalek did unto thee by the way, when ye were come forth out of Egypt; How he met thee by the way, and smote the hindmost of thee, [even] all [that were] feeble behind thee, when thou [wast] faint and weary; and he feared not God. Therefore it shall be, when the LORD thy God hath given thee rest from all thine enemies round about, in the land which the LORD thy God giveth thee [for] an inheritance to possess it, [that] thou shalt blot out the remembrance of Amalek from under heaven; thou shalt not forget [it].Deu 25:17-19

Not long after Israel's first king had been anointed, the moment arrived to eradicate Amalek. It had been about four centuries since the incident at Rephidim and the Amalekites had continued attacking Israel over the years (Judg 6:3, 10:12; 1 Sam 14:48).

An expression, not biblical, now comes to mind: The mills of God grind slowly, yet they grind exceeding fine. God never forgets to exercise justice, and in his providence he may begin with his own people. In this way, the refining retributions sift his own household (1Pet 4:17), even as they punish his enemies. So it was with King Saul. He had disappointed the Lord by his disobedience at Gilgal, and was sifted in the matter of annihilating the Amalekites. Again he disobeyed, and thus was rejected as king though his reign did not in fact end at the time.

At Gilgal, Saul offered the burnt offering rather than waiting for Samuel to do so. (1 Sam 13:9-14) Samuel warned him then …thy kingdom shall not continue: the LORD hath sought him a man after his own heart(vs 14).

Again, when instructed to destroy the Amalekites, Saul disobeyed and disappointed. The Lord said to him through his prophet, I remember [that] which Amalek did to Israel, how he laid [wait] for him in the way, when he came up from Egypt. Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass.(1 Sam 15:2, 3) But Saul spared the Amalekite king Agag and the best of the sheep, oxen and lambs. He only destroyed what he considered to be vile.

Then the Lord told Samuel he was sorry he had made Saul the king, and Samuel reprimanded Saul,

Hath the LORD [as great] delight in burnt offerings and sacrifices, as in obeying the voice of the LORD? Behold, to obey [is] better than sacrifice, [and] to hearken than the fat of rams. For rebellion [is as] the sin of witchcraft, and stubbornness [is as] iniquity and idolatry. Because thou hast rejected the word of the LORD, he hath also rejected thee from [being] king.(1 Sam 15:22, 23)

Another expression comes to mind: The Lord is doing many things at one time. In this incident, He punished Amalek severely while proving Saul was unfit for command, and importantly, he arranged a lesson for us, To obey is better than sacrifice. This brings up a question: Am I willing to remove or destroy the object or subject in my surroundings that offends the Lord?

In the passage cited, many things are equated with disobedience: rebellion, witchcraft, stubbornness, iniquity, idolatry and rejection of God's Word. Though presumably sparing many sheep for the purpose of sacrificing them in thankfulness to God, Saul failed in his mission. He attributed the oversight to his followers (1 Sam 15:24), but is held responsible for failing to command them.

Obedience is required in all things, particularly in offering sacrifices properly. In Old Testament days, a king was never to usurp the role of the priest; likewise, for us in New Covenant days, there must be a godly presentation and handling of the doctrine of Christ's perfect sacrifice. If a pastor were to tell us he could forgive our sins or that our sins could be forgotten if we would follow a prescribed regimen of prayer, Bible reading or good works, he would be mishandling truth and promoting error.

A last expression is pertinent, this one from the Bible: To whom much is given, much will be required.(Luke 12:48) In context, this passage speaks of a servant who knew the right thing to do, but did not do it. The one who is aware of God's laws and specific commands will be held fully responsible for complete obedience. Those less knowledgeable will enjoy lenience. Leaders are doubly responsible to set an example in obedience. They have power to guide people into truth or into error.